A Critique of a Popular Teaching Illustration

There is a graphic that is being used in some recent singing
schools, and shared in social media, showing the major scale and
the minor scale together, in one long sequence of notes. Here is
what it looks like:
The hitch with this otherwise lovely illustration is that it is
incorrect. It shows the Major scale as Sacred Harp singers sing
it, with the correct intervals between each note, but the Minor
scale is wrong. Initially it seems like such a wonderful way to
show how to get from the major to the minor; simply sing down two
notes from the Major scale tonic note to land on the Minor scale
tonic note. Indeed, page 18 of the Rudiments (The
Sacred Harp, Denson edition, 1991) seems to suggest this
very illustration: "The natural
minor scale can be constructed from the major scale by moving
the tonic from Fa down to La." But one needs to read the
entire paragraph, for the above illustration does not show what
all Sacred Harp singers do when they reach the 6th note of the
minor scale.* Rather, they do what is shown below:

Of course, in this second illustration the Major scale 4th note is
displayed incorrectly. Sigh... the first illustration does not
display the two Sacred Harp scales as they are sung, merely as
they are printed in the songs in the songbook. Neither
illustration should used when
teaching the scales. If new singers try to learn how to
sing the Minor scale from the first illustration, they will be
learning it wrong, and if from the second illustration they'll be
learning the Major scale wrong.

The best course for teachers is to use separate scales. If their
choice for the Minor scale is to show it (without any displayed
key signature) starting on D and ending on D, all the better...
Their keyboard-owning students can then practice plunking it out
and will come much closer to getting the correct intervals into
their heads.

*In the Rudiments in the 1991 edition of The
Sacred Harp (Denson edition), see paragraph 15 in Chapter
III Melodics, and paragraph 4 in Chapter IV Keys.